It has long been known in the disposable absorbent bandage art that it is extremely desirable to construct absorptive devices, such as disposable diapers, sanitary napkins, incontinent devices, absorbent wound dressings, and the like, presenting a dry cloth-like surface feel to the user's skin at any anticipated points of contact, e.g., as topsheets and/or backsheets.
While woven and non-woven fibrous webs are often employed for this purpose because of their pleasant surface feel, polymeric webs have been shown to exhibit more desirable fluid transport and fluid restraining characteristics in many circumstances.
It is, of course, known in the art to employ polymeric webs as both fluid pervious topsheets and fluid impervious backsheets on bandage structures. For example, U.S. Pat. No. 3,911,187 issued to Raley on Oct. 7, 1975 discloses a fluid impervious thermosplastic film suitable for use as a backsheet in structures such as disposable absorbent bandages, said film having a permanently embossed design which allegedly simulates woven fabric or cloth and which has edge curl resistance under machine stress. The embossed design is made up of latitudinally and longitudinally alternating hollow protuberances and depressions on both sides of the film. The width of the protuberances at their base vary from 5 mils to about 50 mils, most preferably from about 5 mils to about 20 mils. In the disclosed embodiment, the protuberances are comprised of a multiplicity of planar wall segments.
U.S. Pat. No. 4,343,848 issued to Leonard, Jr. on Aug. 10, 1982 discloses another fluid impervious embossed thermoplastic film suitable for use as a backsheet, said film being characterized in that one surface thereof is provided with a plurality of rows of protuberances having the shape of pyramids with square bases which extend perpendicular to both the longitudinal and the transverse axes of the film. The protuberances are joined at the edge of the bases by flat valley portions which intersect each other at right angles. It is alleged that the embossed film has a low coefficient of friction and increased embossed thickness. The protuberances in the disclosed embodiment preferably have a base from 4 mils to about 10 mils and a height from about 1/2 mil to about 4 mils. In the disclosed embodiment, the pyramids are comprised of substantially planar wall segments.
The use of fluid pervious polymeric webs as topsheets is also well known in the art. For example, U.S. Pat. No. 3,814,101 issued to Kozak on June 4, 1974, suggests the use of a fluid pervious hydrophobic film provided with a plurality of valvular slits which restrict the reverse flow of liquid from the absorbent element of the device as a topsheet for a disposable absorbent bandage.
For the purpose of interpreting the present specification and claims, the term "macroscopically expanded", when used to describe three-dimensional plastic webs, ribbons and films of the present invention, refers to webs, ribbons and films which have been caused to conform to the surface of a three-dimensional forming structure so that both surfaces thereof exhibit a three-dimensional pattern of surface aberrations corresponding to the macroscopic cross-section of said forming structure, the surface aberrations comprising said pattern being individually discernible to the normal naked eye, i.e., a normal eye having 20/20 vision unaided by any instrument that changes the apparent size or distance of an object or otherwise alters the visual powers of the eye, when the perpendicular distance between the viewer's eye and the plane of the web is about 12 inches. Such macroscopically expanded webs, ribbons and films are typically caused to conform to the surface of said forming structure by embossing, i.e., when the forming structure exhibits a pattern comprised primarily of male projections, by debossing, i.e., when the forming structure exhibits a pattern comprised primarily of female capillary networks, or by extrusion of a resinous melt directly onto the surface of a forming structure of either type. Also for the purpose of interpreting the present specification and claims, the term "planar", when utilized herein to describe plastic webs, ribbons and films of the present invention, refers to the overall condition of the web, ribbon or film when viewed by the normal naked eye on a macroscopic scale. In this context "planar" webs, ribbons and films may include webs, ribbons and films having a fine scale, yet visible, pattern of surface aberrations on one or both sides thereof, the surface aberrations comprising said visible pattern not being individually discernible to the normal naked eye when the perpendicular distance between the viewer's eye and the plane of the web is about 12 inches.
U.S. Pat. No. 3,929,135 issued to Thompson on Dec. 30, 1975, discloses one exemplary prior art fluid pervious, macroscopically expanded three-dimensional topsheet comprised of liquid impermeable material, but provided with tapered capillaries, said capillaries having a base opening in the plane of the topsheet and an apex opening remote from the plane of the topsheet, said apex opening being in intimate contact with the absorbent pad utilized in the disposable absorbent bandage.
Macroscopically expanded polymeric webs employing features to reduce gloss and improve tactile impression are also disclosed in the prior art, as is the use of such webs as topsheets and/or backsheets in disposable absorbent bandages. For example, commonly assigned U.S. Pat. No. 4,327,730 issued to Sorensen on May 4, 1982 discloses a disposable diaper having a fluid pervious textured topsheet of thermoplastic material. The topsheet is macroscopically expanded and is provided with a multiplicity of nubbles across its surface. The nubbles do not substantially alter the macroscopic profile of the film, but do impart a more cloth-like tactile impression and reduced gloss to the film.
An improved macroscopically expanded three-dimensional polymeric web exhibiting a substantially non-glossy visible surface and cloth-like tactile impression is disclosed in commonly assigned U.S. Pat. No. 4,463,045 issued to Ahr et al. on July 31, 1984. If desired, the macroscopically expanded three-dimensional polymeric web of Ahr et al. may be used as as fluid pervious topsheet in a disposable absorbent bandage. The visible surface of the macroscopically expanded three-dimensional polymeric web of Ahr et al. is preferably provided with a regularly spaced, microscopic pattern of surface aberrations, said pattern being too fine to be discernible by the normal naked eye when the perpendicular distance between the viewer's eye and the plane of the web is about 12 inches, but which pattern of surface aberrations is highly effective in substantially eliminating specular reflection of incident light. Said webs may be produced by means of a one sided forming process wherein said surface aberrations are transmitted through the thickness of the web during processing or by means of a two sided forming process wherein said surface aberrations are imposed directly onto the visible surface of the web. The surface aberrations may comprise either protuberances projecting generally outwardly from the surface of the web or depressions projecting generally inwardly from the surface of the web, e.g., the knuckle pattern of a fine woven wire embossing member. Macroscopically expanded three-dimensional polymeric webs of the type disclosed in the patent to Ahr et al. are often employed as alternatives for cloth and fiber structures which contact the wearer's skin.
The patent to Ahr et al. teaches the criteria which must be met with respect to the regularly spaced pattern of surface aberrations in order to diffusely reflect incident light and thereby eliminate gloss. It further teaches that in those situations where a more cloth-ike or fiber-like tactile impression in the resultant macroscopically expanded three-dimensional plastic web is also desired, the surface aberrations in the web should preferably exhibit an average amplitude of at least about 0.2 mils (i.e., 0.0002 inches), and most preferably at least about 0.3 mils (i.e., 0.0003 inches). According to Ahr et al., a more cloth-like or fiber-like tactile impression is percieved in macroscopically expanded three-dimensional plastic webs which meet the aforementioned amplitude criteria whether the surface aberrations comprise protuberances or depressions due to the fact that in either case the surface of the web is divided into at least two distinct planes separated from one another by a distance of at least 0.2 mils (i.e., 0.0002 inches). In the case of protuberances, it is the tops of the aberrations which contact the observer's skin, while in the case of depressions it is the substantially planar surface in which said aberrations originate which contacts the observer's skin. Ahr et al. further suggests that because said division is carried out in a fine microscopic pattern, only the reduced area of contact with the uppermost surface of the web and not existence of the pattern is tactually perceived.
Because of the superior fluid and vapor handling characteristics which can be provided in polymeric webs of the aforementioned type and their inherent cost advantages when contrasted to woven and non-woven fibrous webs, considerable effort has been expended to improve the consumer's reaction to the use of polymeric webs in contact with the skin. While much progress has been demonstrated in eliminating the negative consumer reaction to placing polymeric webs comprised of plastic in contact with the user's skin, particularly with respect to webs following the teachings of the aforementioned Ahr et al. patent, the approach generally taken has been to macroscopically expand the webs using three-dimensional patterns which make the web look more like a fibrous or cloth structure. Examples of this technique are the webs disclosed in commonly assigned U.S. Pat. No. 4,342,314 issued to Radel and Thompson on Aug. 3, 1982. While such webs are generally at parity with fibrous or cloth structures in terms of visual and tactile acceptance by consumers, it is an object of the present invention to provide both "planar" polymeric webs and "macroscopically expanded" polymeric webs exhibiting a visual and tactile impression which is generally consumer prefererd when contrasted to woven and non-woven fibrous webs of comparable macroscopic profile.
It is another object of the present invention to provide webs of the aforementioned type which exhibit fluid-handling and breatheability characteristics not obtainable with woven or non-woven fibrous webs, nor even with prior art polymeric webs.
It is another object of the present invention to provide disposable absorbent bandage structures which employ either "planar" or "macroscopically expanded" plastic webs of the present invention with a high level of consumer preferance over similar absorbent bandage structures employing either woven or non-woven fibrous webs or non-microapertured polymeric webs of the prior art.